Corrosion of 304SS in H₂SO₄ containing molybdates and tungstates as inhibitors

The electrochemical behavior of 304 stainless steel has been thoroughly investigated in H₂SO₄ as a function of H₂SO₄, chloride ions, and molybdate ions concentrations at room temperature. In addition, the effects of other ions such iodide, bromide, and tungstate ions have been studied. Standard corrosion techniques that have been used include Tafel measurements, R_p vs. time measurements, cyclic polarizations measurements, and the critical pitting potential measurements. Initial results indicate that the addition of molybdate ions at sufficient concentrations enhances both the resistance to general corrosion and to pitting corrosion in the case of chloride ions presence. It is suggested that molybdate ions inhibit pitting by lowering the current densities in the active and passive range, enhancing repassivation in the process, making it difficult for metastable pits to grow into stable ones.